The present invention relates to a storage unit, a storage unit control method, and a storage system.
Data is backed up so that the original data can be restored when data stored in a storage unit is lost. This data backup is usually performed by storing a copy of data, stored in a storage unit, also in a backup storage unit.
A technology for backing up data using the replication technology has also been developed. Replication is a technology for writing data on two storage units, connected communicably to each other, in such a way that, when data is written on one storage unit, a copy of the data is sent to the other storage unit and is written also on the other storage unit.
JP-A-2002-259183 and the corresponding U.S. patent application publication No. 2002/0169925A1 discloses an example of a storage unit.